1. Field of the invention:
The present invention relates to an electric shutter for cameras and, more particularly, to an opening and closing means for an electric shutter arranged to open and close shutter blades during the time when an actuating member moves in one direction.
2. Description of the prior art:
Conventional opening and closing means for electric shutters are arranged, for example, as follows. That is, separate actuating members, one of which being exclusively for opening of shutter blades and the other being for closing of shutter blades, and actuating power sources respectively connected to said actuating members are provided. When cocking the shutter, the above-mentioned two actuating power sources are charged at the same time and the above-mentioned two actuating members are locked by an opening release member and closing release member respectively.
Said kind of opening and closing means requires two actuating power sources as described in the above and, at the same time, two release members have to be provided. Consequently, the mechanism of such opening and closing means becomes complicated, the cost of production becomes high and the overall structure becomes large. Moreover, if the closing release member is directly engaged with an electro-magnet as an armature in said type of opening and closing means, a gap sometimes occurs between the closing release member serving as an armature and electro-magnet because of an impact caused when the cocking member returns, for example in case of such opening and closing means for a shutter for which shutter cocking operation is carried out in combination with film winding operation of the camera, because of the relation to the other related members and, consequently, misoperation is sometimes caused by the above. Therefore, an armature member engageable with the closing release member is generally provided separetely so that it contacts the electro-magnet, and movement is transmitted to the closing actuating member through the closing release member. As a result, however, construction of the opening and closing means becomes more complicated.
On the other hand, regarding the power switch, there has been a problem as described below. That is, if the power switch is arranged relative only to the release member of the camera, the electric power source of the exposure control circuit is turned off when the pressure to the release member is released halfway in case of a long-time exposure. As a result, proper exposure is not attained. To solve the above problem, it is known to provide one switch relative to the release member and, at the same time, to provide another switch relative to a part of the shutter mechanism, said two switches being connected in series or parallel. In such arrangement, it is necessary to accurately adjust the opening and closing timing of two switches and the number of required parts becomes large. Consequently, the cost of production becomes high.